Refrigerant flow control for a refrigeration system



Nov. 17, 1959 E. P. PALMATIER 2,912,831

REFRIGERANT FLOW CONTROL FOR A REFRIGERATION SYSTEM Filed'Feb. 9, 1955 2 Sheets-Sheet 1 FIG.|

; IN V EN TOR.

' EVERETT F! PALMATIER 7 BY X2 Nov. 17,.1959 E. P. PALMATIER 2,

REFRIGERANT FLOW cou'mor. FOR A REFRIGERATIONISYSTEM Filed Feb. 9, 1955 2 Sheets-Sheet 2 FIG.2

' INVENTOR.

EVERETT R PA LMATIER BY XMWJ'M United States Patent..-O

REFRIGERANT FLOW CONTROL FOR A REFRIGERATION SYSTEM Everett P. Palmatier, Solvay, N.Y., assiguor to Carrier Corporation, Syracuse, N.Y., a corporation of Delaware 7 Application February 9, 1955, Serial No. 487,016

9 Claims. (Cl. 62-113) This invention relates broadly to refrigeration systems and more particularly to a refrigerant flow control for a refrigeration system of the type having a fixed restriction in the liquid line connecting the condenser and the evaporator.

A refrigeration system of the kind under consideration includes the usual components such as a compressor, a condenser, an evaporator and lines interconnecting the elements to form a. closed circuit for the flow of refrigerant. The circuit includes in the line connecting the evaporator and the condenser, a fixed restriction in the form of an orifice or a section of tubing having a diameter less than the diameter of theconduit forming the liquid line.

One of the problems associated with the use of the arrangement described involves maintaining proper flow of refrigerant under varying condenser temperature and pressure. It will be understood that flow of refrigerant though the capillary is dependent upon a pressure drop across the capillary tube. One factor affecting the pressure drop is a variation in the operating pressure of. the

condenser occasioned by a change in the condensing tem-' 5 perature as the temperature of the coolant varies.

Accordingly, it is the chief object of this invention to provide a refrigerant flow control operative over a range of condensing pressures. This objective is accomplished by causing a variation in the exchange of heat This causes liquid to back;

manner as to maintain essentially constant liquid levelu in the receiver element.

Another object of the invention includes the provision of an arrangement of the type described wherein a connection is established between a section of the discharge line and a receiver located between the capillary tube;

and the condenser, the purpose of the connection being to permit flow of a portion of the refrigerant in the receiver to the discharge line at a point upstream from the locale' of heat exchange between the discharge line and the yided with a fixed restriction or capillary tube 18.

7 2,912,831 Patented Nov. 17, 1959 a refrigeration system is illustrated, '10 represents a conventional motor driven compressor. Condenser 13 is shownconnected to the compressor 10 by discharge line 14. Located in the discharge line' 14 is a Venturi device 15 for the purpose of defining a portion of the discharge line having a pressure relatively lower than condensing pressure. Liquid line 16 connects the condenser 13 and the evaporator 17. A portion of the liquid line is-prtX receiver-19 is placed in the liquid line 16 between the condenser 13 and the capillary 18. Line 20 connects the receiver and the Venturi device 15 as shown in Figure 1. Thecapillary 18 is shown in heat exchange relation with a portion of the hot gas discharge line. Suction line 21 connects the evaporator and the compressor to complete the refrigeration circuit.

Considering the operation of the system, refrigerant in the gaseous state is withdrawn from the evaporator 17 through line 21, compressed in the compressor 10 and forwarded to the condenser 13 through line 14. The gaseous refrigerant is converted to the liquid state in the condenser as an exchange of heat between the refrigerant and a cooling medium, such as air, occurs. frigerant is then forwarded to the evaporator through the capillary 18 and converted to the gaseous state as .an exchange of heat between a medium to be cooled and the refrigerant occurs.

With the construction described, the Venturi device 15 creates a Zone of pressure lower than the pressure existing in the receiver so that refrigerant flows either in the gaseous or liquid phase from the receiver to the discharge line, for subsequent passage in heat exchange :relation with the capillary. The location of the connection between line 20 and the receiver is determined by system considerations. For example, at design conditions a certain level of liquid refrigerant may be expected in, the receiver. If the condensing pressure is increased :as for example, through an increase in the temperature of the cooling medium, the level of the liquid refrigerant will drop in the receiver below the connection between the receiver and the line 20. Refrigerant in the vaporous phase having a temperature equal or slightly above the ,condensing temperature will flow into the Venturi device to mix with the superheated gas flowing from the compressor. l

-,The mixture of gases at a relatively high temperature transfers heat to the capillary tube. Since the capillary is then at a higher temperature, a greater portion of the liquid refrigerant passing therethrough undergoes a change in stateor" conversion to gas, thus creating increased resistance to liquid flowing to the evaporator. Since there is increased resistance ot liquid flow to the evaporator,

the amount of liquid in the receiver will tend to increase, raising the liquid level in the receiver to the point of the connection with the Venturi device.

; -When the condensing pressure decreases, liquid will "backup in the receiver until liquid refrigerant flows capillary. The gas in the hot gas line is cooled bythe refrigerant passing from the receiver. The extent of the cooling or desuperheating of the hotv gas depends of course on the state and temperatureof the refrigerant .flowing from the receiver.

Other objects and advantages of the invention will be,

from the connection with the receiver through line 20 to Venturi device 15.- The liquid refrigerantfflashes off and cools the superheated gas to a temperature approaching saturation temperature or the temperature of liquid leaving the receiver. In other words, the liquid refrigerant mixing with the superheated gas desuperheats the gas. 7 Since the gas is desuperheated little or no heat exchange takes place between the gaseous .refrigerant and v refrigerant in the capillary tube, the temperature of refrigerant in the discharge line being less than in the case where .gaseous refrigerant passes to the Venturi device Figure 2 is a diagrammatic view of a refrigeration" Referring more particularly to the drawings wherein .from'the receiver, so that less gas is formed in the capillary. This reduces the liquid level in the receiver until it is again at the point of the connection with the Venftfuri device. in other words, the heating effect on the Liquid re- Q3 capillary tube is controlled by the level of liquid refrigerant in the receiver so that a balance will always be maintained.

Figure 2 illustrates the liquid level control of the present invention applied to a refrigeration system in which a line 21 is provided to connect the condenser 13 directly with the Venturi device 15. It will be appreciated that in the system illustrated in Figure 2, the receiver is omitted.

The present invention provides a simple liquid level control for the capillary tube of a refrigeration system. The system employing the present liquid level control is substantially self balancing to maintain a desired level of liquid refrigerant in the receiver or condenser. The invention provides an economical high side liquid level control for a refrigeration system which assures desired feed of liquid refrigerant to the evaporator even when the load imposed on the evaporator varies from design conditions.

While I have described a preferred embodiment of the invention, it will be understood the invention is not limited thereto since it may be otherwise embodied within the scope of the following claims.

I claim:

1. in a refrigeration system including a compressor; a condenser; a discharge line connecting the compressor and the condenser; an evaporator; a liquid line connecting the condenser and evaporator; a restriction in the liquid line, said restriction having a portion in heat exchange with the discharge line, and a suction line connecting the evaporator and the compressor to complete a circuit for the fiow of refrigerant, a receiver disposed in the liquid line upstream from said restriction, a restriction in the discharge line defining an area having a pressure lower than the pressure in the receiver and a line connecting the receiver and the discharge line restriction to provide refrigerant fiow between the parts.

2. A refrigeration system comprising an evaporator, a compressor, a line connecting the evaporator and the compressor, a condenser, a discharge line connecting the compressor and the condenser, a liquid line connecting the condenser and the evaporator, said liquid line having a fixed restriction therein, a receiver in the liquid line between the condenser and the fixed restriction, said discharge line including a restriction creating a zone in the discharge line having a pressure lower than the pressure in the receiver, said discharge line having a portion thereof between the low pressure zone and the condenser in heat exchange relation with at least a portion of the fixed restriction, and a line connecting the receiver and the low pressure zone of the discharge line permitting flow of refrigerant from the receiver to the discharge line.

3. The method of controlling the flow of refrigerant through a restriction in the liquid line of refrigerating system including an evaporator, a compressor, a suction line connecting the evaporator and the compressor, a condenser, a discharge line connecting the compressor and the condenser which consists in the steps of providing an exchange of heat between refrigerant in a portion of the discharge line remote from the condenser and refrigerant in a portion of the liquid line restriction and varying the rate of heat transfer in accordance with variations in liquid level in the high side of the refrigeration system.

4. The method of controlling the flow of refrigerant through a restriction in the liquid line of a refrigerating system including an evaporator, a compressor, a suction line connecting the evaporator and the compressor, a condenser, a discharge line connecting the compressor and the condenser which consists in the steps of providing an exchange of heat between refrigerant in a portion of the discharge line remote from the condenser and refrigerant in a portion of the liquid line restriction and varying the temperature of the refrigerant in the discharge line upstream from the location of heat transfer.

5. The method of controlling refrigerant flow through a restriction in the liquid line of a refrigeration system including a compressor, a condenser, a discharge line connecting the compressor and the condenser, and an evaporator, which consists in the steps of placing refrigerant in a portion of the discharge line in heat exchange relation with refrigerant in the restriction, varying the heating effect imposed upon refrigerant in the restriction by introducing a stream of condensed refrigerant into the stream of gaseous refrigerant in the discharge line before it is placed in heat exchange relation with refrigerant in the restriction.

6. The method of controlling the flow of refrigerant through a restriction in the liquid line of a refrigeration system of the type including a compressor, hot gas discharge line, condenser, liquid line, evaporator and suction line interconnected to form a circuit for the flow of a volatile refrigerant which consists in the steps of providing a zone in the discharge line having a pressure lower than the condensing pressure, placing refrigerant in a portion of the discharge line downstream from said zone in heat exchange relation with refrigerant in the liquidline restriction, and regulating the heat transfer action by introducing refrigerant that has been subjected to the cooling action of the condenser into the low pressure zone in the discharge line.

7. A refrigeration system comprising a compressor, a condenser, a discharge line connecting the compressor and the condenser, an evaporator, a liquid line connecting the condenser and the evaporator, a suction line connecting the evaporator and the compressor, refrigerant fiow restricting means interposed in the liquid line and having at least a portion thereof in heat exchange relation with a portion of the discharge line, and means for varying the temperature of the discharge line refrigerant upstream of the portion of the line in heat exchange relation with the refrigerant restricting means to regulate the heat exchange action in the refrigerant restricting means and thus to control the flow of refrigerant through said restricting means.

8. The system described in claim 7 wherein said last mentioned means includes a Venturi device interposed in said discharge line upstream of the portion of the discharge line in heat exchange relation with the restricting means, and a line connected to the Venturi device and a portion of the high side of the system downstream of the portion in heat exchange relation with the restricting means whereby flow of refrigerant from the compressor in the discharge line induces flow of refrigerant having a lower temperature than that emanating from the compressor into the discharge line.

9. A refrigeration system comprising a compressor, a condenser, a discharge line connecting the compressor and the condenser, an evaporator, a liquid line connecting the condenser and the evaporator, a suction line connecting the evaporator and the compressor, refrigerant flow restricting member interposed in said liquid line,

' said member having a portion thereof in heat exchange relation with a portion of the discharge line whereby heat sufficient to vaporize a portion of the liquid flowing through the refrigerant flow restricting member is trans ferred from the discharge line to the flow restricting means and means responsive to an operating characteristic of the condenser for varying the temperature of the refrigerant in the discharge line by introducing either gaseous or liquid refrigerant from the condenser into the discharge line to regulate the heat exchange action and control the fiow of refrigerant through the member.

References Cited in the file of this patent UNITED STATES PATENTS 2,022,774 Kucher Dec. 3, 1935 2,300,086 Alsing Oct. 27, 1942 2,359,595 Urban Oct. 3, 1944 2,404,112 Urban July 16, 1946 

